182. advanced non-equiatomic fenicoalcrb high entropy alloy with heterogeneous lamella structure showing high strength and good ductility

Department: NanoEngineering
Faculty Advisor(s): Kenneth S. Vecchio

Primary Student
Name: Cheng Zhang
Email: chz040@ucsd.edu
Phone: 858-900-7052
Grad Year: 2018

Student Collaborators
Chaoyi Zhu, chz132@eng.ucsd.edu

Due to unique and attractive engineering properties, High Entropy Alloys (HEAs) have attracted great attention over the last one decade. In the previous studies, in order to obtain high strength and good ductility, solid-solution strengthening and precipitation strengthening are frequently employed. However, apart from the refining grain size method, research in the structure design of HEAs is rarely conducted. In our study, advanced Fe-Ni-Co-Al-Cr-B (NCACB) HEA fabricated with heterogeneous lamella (HL) structure through novel thermomechanical processing shows high strength(UTS is about 700MPa) and good ductility (total elongation is around 35%). When compared with fine-grained samples, over 50% increase in the elongation can be achieved in HL NCACB with only about 15% reduction in UTS. And in comparison with coarse-grained specimens, nearly 80% increase in UTS can be obtained in HL NCACB with less than 15% reduction in the elongation. In the current study, NCACB HL HEA designed by CALPHAD method was made by conventional methods, including arc melting, hot rolling, cold rolling and annealing. By precisely controlling the parameters during the thermomechanical processing, heterogeneous structure can be obtained in NCACB. The combination of high strength and good ductility in HL NCACB provides a brand new method for the improvement in mechanical properties of HEAs. The research incorporates many of the most advanced materials characterization tools and techniques, including scanning electron microscopy integrated with energy dispersive x-ray spectroscopy and electron backscattered diffraction, as well as STEM microanalysis, and x-ray diffraction. These tools and techniques are available in the NanoEngineering Materials Research Center [NE-MRC], and are utilized here to analyze the phase, microstructure, grain size, and grain texture of these samples.

Industry Application Area(s)
Aerospace, Defense, Security | Materials

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